fuzzy-aho-corasick

A high-performance, Unicode-aware, safe-Rust implementation of the Aho–Corasick automaton extended with fuzzy matching — insertions, deletions, substitutions, and transpositions — over grapheme clusters, with optional case-insensitive folding.

It answers the question “where in this text do any of my patterns appear, allowing for a few typos?” — the kind of problem that shows up in entity/name matching (e.g. AML screening), OCR cleanup, search-as-you-type, and log/stream scanning.

What it does

• Exact and fuzzy multi-pattern matching in one pass over a shared trie, with Levenshtein-style edits plus transposition.
• Unicode correctness: it matches over grapheme clusters, not bytes or code points, and folds case in a Unicode-aware way.
• Tunable scoring: per-edit-type penalties, a character similarity table, per-pattern weights, and a similarity threshold decide what counts as a match and how matches rank.
• Rich output control: raw matches, several ranking strategies, non-overlapping selection, segmentation, splitting, and find-and-replace.
• Scales to streams: search or replace over any Read/Write in constant memory, single- or multi-threaded.
• Optional fast lane: an opt-in bit-parallel pre-filter skips regions that provably cannot match, for a large speedup on big, sparse inputs — with identical results.

How to read this book

• Getting Started gets you matching in a couple of minutes.
• Core Concepts explains the edit model and how scores are computed — read this once and the rest of the API makes sense.
• Building an Engine, Searching, and Similarity cover the configuration surface.
• Streaming and Performance are for larger or latency-sensitive workloads.
• Reference describes how the engine works internally and credits the underlying research.

The crate’s API documentation on docs.rs is the authoritative reference for every type and method; this book is the narrative guide.